Monoclonal antibodies with enhanced adcc function

ABSTRACT

The invention concerns a method for obtaining and selecting monoclonal antibodies by an ADDC-type test, said antibodies capable of activating type III Fcy receptors and having a particular glycan structure. The inventive anti-D antibodies can be used for preventing Rhesus isoimmunisation in Rh negative persons, in particular for haemolytic disease in a new-born baby of for uses such as idiopathic thrombocytopenic pupura 9ITP)

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/157,061 filed Jan. 16, 2014, which is a continuation of U.S.application Ser. No. 13/077,644 filed Mar. 31, 2011, now U.S. Pat. No.8,685,725, issued on Apr. 1, 2014, which is a continuation of Ser. No.11/039,877, filed Jan. 24, 2005, now U.S. Pat. No. 7,931,895, issued onApr. 26, 2011, which is a divisional of U.S. application Ser. No.10/257,477, filed Jan. 14, 2003, now U.S. Pat. No. 7,579,170, issued onAug. 25, 2009, which is a U.S. National Stage of Internationalapplication serial number PCT/FR01/01127, filed Apr. 12, 2001, whichclaims priority to France application serial number 00/04,685, filedApr. 12, 2000, all of which are incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a method of obtaining and selectingmonoclonal antibodies using an assay of the ADCC type, said antibodiesbeing capable of activating Fcγ type III receptors. The invention isalso directed toward monoclonal antibodies having a particular glycanstructure, the cells producing said antibodies, the methods forpreparing the producer cells, and also the pharmaceutical compositionsor the diagnostic tests comprising said antibodies. The anti-Dantibodies according to the invention can be used for preventing Rhesusisoimmunization of Rh-negative individuals, in particular a hemolyticdisease of the newborn (HDN), or in applications such as IdiopathicThrombocytopenic Purpura (ITP).

Passive immunotherapy using polyclonal antibodies has been carried outsince the 1970s. However, the production of polyclonal immunoglobulinsposes a problem: The immunization of volunteers was discontinued inFrance in 1997 because of the ethical problems that such acts present.In France, as in Europe, the number of immunized donors is too low toensure a sufficient supply of certain antibodies, to such an extent thatit proves necessary to import hyperimmunized plasma from the UnitedStates for example.

Thus, this immunoglobulin shortage does not make it possible to envisageantenatal administration for preventing HDN.

Various studies have resulted in the production of human monoclonalantibodies for the purpose of replacing the polyclonal antibodiesobtained from fractionating plasmas from voluntary donors.

Monoclonal antibodies have several advantages: they can be obtained inlarge amounts at reasonable costs, each batch of antibodies ishomogeneous and the quality of the various batches is reproducible sincethey are produced by the same cell line, which is cryopreserved inliquid nitrogen. It is possible to ensure the safety of the product withregard to an absence of viral contamination.

Several publications describe the production of cell lines producinghuman anti-Rh D monoclonal antibodies of IgG class, from B cells ofimmunized donors. Boylston et al. 1980; Koskimies 1980; Crawford et al.1983; Doyle et al. 1985; Goossens et al. 1987; Kumpel et al. 1989(a) andMcCann-Carter et al. 1993 describe the production of B lymphocyte linestransformed with the EBV virus. Melamed et al. 1985; Thompson et al.1986 and McCann-Carter et al. 1993 relate to heterohybridomas resultingfrom B lymphocyte (transformed with EBV)×murine myeloma fusion. Goossenset al., 1987 relates to heterohybrids resulting from B lymphocyte(transformed with EBV)×human myeloma fusion. Bron et al., 1984 and Founget al., 1987 describe heterohybrids resulting from B lymphocyte(transformed with EBV)×human-mouse heteromyeloma fusion and, finally,Edelman et al., 1997 relates to insect cells transfected with the geneencoding an anti-Rh(D) using the baculovirus system.

Among the patents and patent applications relating to such monoclonalantibodies and the lines secreting them, mention may be made of: EP576093 (AETS (FR), Biotest Pharma GmbH (Germany); Composition forprophylaxis of the haemolytic disease of the new-born comprises twohuman monoclonal antibodies of sub-class IgG1 and IgG3, which are activeagainst the Rhesus D antigen), RU 2094462, WO 85/02413 (Board ofTrustees of the Leland Stanford Jr. University, Human MonoclonalAntibody against Rh (D) antigen and its uses), GB 86-10106 (CentralBlood Laboratories Authority, Production of heterohybridomas formanufacture of human monoclonal antibodies to Rhesus D antigen), EP 0251 440 (Central Blood Laboratories Authority, Human Anti-Rhesus DProducing Heterohybridomas), WO 89/02442, WO 89/02600 and WO 89/024443(Central Blood Laboratories Authority, Human Anti-Rh (D) MonoclonalAntibodies), WO 8607740 (Institut Pasteur, Protein Performance SA,Paris, FR, Production of a recombinant monoclonal antibody from a humananti-rhesus D monoclonal antibody, production thereof in insect cellsand uses thereof), JP 88-50710 (International Reagents Corp., Japan,Reagents for Determination of Blood Group Substance Rh (D) Factor), JP83-248865 (Mitsubishi Chemical Industries Co., Ltd., Japan, Preparationof Monoclonal Antibody to Rh (D) positive Antigen); CA 82-406033 (QueensUniversity at Kingston, Human Monoclonal Antibodies) and GB 8226513(University College London, Human Monoclonal Antibody against Rhesus DAntigen).

While the use of monoclonal antibodies has many advantages compared tothe use of pools of polyclonal antibodies, it may, on the other hand,prove to be difficult to obtain an effective monoclonal antibody. Infact, it has been found, in the context of the invention, that the Fcγfragment of the immunoglobulin obtained must have very particularproperties in order to be able to interact with and activate thereceptors of effector cells (macrophage, TH lymphocyte and NK).

The biological activity of certain G immunoglobulins is dependent on thestructure of the oligosaccharides present on the molecule, and inparticular on its Fc component. IgG molecules of all human and murinesubclasses have an N-oligosaccharide attached to the CH₂ domain of eachheavy chain (at residue Asn 297 for human IgGs). The influence of thisglycan-containing residue on the ability of the antibody to interactwith effector molecules (Fc receptors and complement) has beendemonstrated. Inhibiting glycosylation of a human IgG1, by culturing inthe presence of tunicamycin, causes, for example, a 50-fold decrease inthe affinity of this antibody for the FcγRI receptor present onmonocytes and macrophages (Leatherbarrow et al., 1985). Binding to theFcγRIII receptor is also affected by the loss of carbohydrates on IgG,since it has been described that a nonglycosylated IgG3 is incapable ofinducing lysis of the ADCC type via the FcγRIII receptor of NK cells(Lund et al., 1990).

However, beyond the necessary presence of these glycan-containingresidues, it is more precisely the heterogeneity of their structurewhich may result in differences in the ability to initiate effectorfunctions. Galactosylation profiles which are variable depending onindividuals (human serum IgG1s) have been observed. These differencesprobably reflect differences in the activity of galactosyltransferasesand other enzymes between the cellular clones of these individuals(Jefferis et al., 1990). Although this normal heterogeneity ofpost-translational processes generates various glycoforms (even in thecase of monoclonal antibodies), it may lead to atypical structuresassociated with certain pathological conditions, such as rheumatoidarthritis or Crohn's disease, for which a considerable proportion ofagalactosylated residues have been demonstrated (Parekh et al., 1985).

The glycosylation profile of the purified molecule is the consequence ofmultiple effects, some parameters of which have already been studied.The protein backbone of IgGs, and in particular amino acids in contactwith the terminal N-acetylglucosamine (GlcNAc) and galactose residues ofthe mannose α-1,6 arm (aa 246 and 258 of IgGs), may explain theexistence of preferential structures (galactosylation), as shown in thestudy carried out on murine and chimeric IgGs of different isotypes(Lund et al., 1993).

The differences observed also reveal specificities related to thespecies and to the cell type used for producing the molecule. Thus, theconventional structure of the N-glycans of human IgGs reveals asignificant proportion of bi-antennary types with a GlcNAc residue inthe bisecting position, this being a structure which is absent inantibodies produced by murine cells. Similarly, the sialic acid residuessynthesized by the CHO (Chinese Hamster Ovary) line are exclusively ofthe α-2,3 type, whereas they are of the α-2,3 and α-2,6 type with murineand human cells (Yu Ip et al., 1994). Immunoglobulin production inexpression systems other than those derived from mammals may introducemuch more important modifications, such as the presence of xyloseresidues produced by insect cells or plants (Ma et al., 1995).

Other factors, such as the cell culture conditions (including thecomposition of the culture medium, the cell density, the pH, theoxygenation), appear to have an effect on glycosyltransferase activityin the cell and, consequently, on the glycan structure of the molecule(Monica et al., 1993; Kumpel et al., 1994 b).

Now, in the context of the present invention, it has been found that astructure of the bi-antennary type, with short chains, a low degree ofsialylation, and nonintercalated terminal mannoses and/or terminalGlcNAcs, is the common denominator for glycan structures which conferstrong ADCC activity on monoclonal antibodies. A method for preparingsuch antibodies capable of activating effector cells via FcγRIII, inparticular anti-Rh(D) antibodies, has also been developed.

Blood group antigens are classified in several systems depending on thenature of the membrane-bound molecules expressed at the surface of redblood cells. The Rhesus (Rh) system comprises 5 molecules or antigens:D, C, c, E and e (ISSITT, 1988). The D antigen is the most important ofthese molecules because it is the most immunogenic, i.e. it can inducethe production of anti-D antibodies if Rh-D-positive red blood cells aretransfused into Rh-negative individuals.

The D antigen is normally expressed in 85% of Caucasian individuals,these people are termed “Rh-positive;” 25% of these individuals aretherefore Rh-negative, i.e. their red blood cells do not exhibit any Dantigen. D antigen expression exhibits certain variants which may belinked either to a weak antigenic density, reference is then made toweak D antigens, or to a different or partial antigenicity, reference isthen made to partial D antigens. The weak D characteristic ischaracterized in that it is a normal antigen, but the number of sitesthereof per red blood cell is decreased more or less considerably; thischaracteristic is transmissible according to Mendelian laws. Partial Dphenotypes have been discovered in Rh-D-positive individuals who haveanti-D serum antibodies; these partial D antigens can therefore becharacterized as having only part of the mosaic. Studies carried outwith polyclonal and monoclonal antibodies have made it possible todefine 7 categories of partial D antigens with at least 8 epitopesconstituting the D antigen being described (LOMAS et al., 1989; TIPETT1988).

The importance of anti-Rh D antibodies became apparent with thediscovery of the mechanisms leading to hemolytic disease of the newborn(HDN). This corresponds to the various pathological conditions observedin some fetuses or in some newborn babies when there is a feto-maternalblood group incompatibility which is responsible for the formation ofmaternal anti-Rh D antibodies capable of crossing the placental barrier.In fact, fetal Rh-positive red blood cells passing into an Rh-negativemother can lead to the formation of anti-D antibodies.

After immunization of the Rh-negative mother, the IgG class anti-Dantibodies are capable of crossing the placental barrier and of bindingto the fetal Rh-positive red blood cells. This binding leads to theactivation of immunocompetent cells via their surface Fc receptors, thusinducing hemolysis of the sensitized fetal red blood cells. Depending onthe strength of the reaction, several degrees of seriousness of HDN canbe observed.

An HDN diagnosis can be carried out before and after birth. Prenataldiagnosis is based on the development of the anti-D antibody level inthe mother using several immunohematological techniques. Post-partumdiagnosis may be carried out using an umbilical cord blood sample,analyzing the following parameters: determining the blood groups of thefetus and of the father; searching for anti-D antibodies; assaying thehemoglobin and the bilirubin.

Prophylactic treatment for HDN is currently systematically given to allwomen with an Rh-negative blood group who have given birth to anRh-positive child, with injections of human anti-D immunoglobulin. Thefirst real immunoprophylaxis trials began in 1964. For the prevention tobe effective, the immunoglobulin must be injected before theimmunization, i.e. within the 72 hours following the birth, and theantibody doses must be sufficient (10 μg of anti-D antibodies per 0.5 mlof Rh+ red blood cells).

Several anti-D monoclonal antibodies have been the subject oftherapeutic assessment: BROSSARD/FNTS 1990 (not published);THOMSON/IBGRL 1990; KUMPEL/IBGRL 1994; BELKINA/Institute of hematology,Moscow, 1996; BIOTEST/LFB 1997 (not published). The clinicaleffectiveness of the antibodies in inducing clearance of Rh(D)-positivered blood cells was assessed in Rh(D)-negative volunteers.

A single IgG1 antibody showed an effectiveness equivalent to that ofanti-D polyclonal immunoglobulins, but only in some patients (KUMPEL etal., 1995).

The invention proposes to provide monoclonal antibodies which reply tothe abovementioned problems, i.e. antibodies selected using an assay ofthe ADCC type specific for the antibody and/or the antibodies having aglycan structure required for obtaining good effectiveness.

SUMMARY OF THE INVENTION

Thus, the present invention relates to a method for preparing amonoclonal antibody capable of activating effector cells expressingFcγRIII, characterized in that it comprises the following steps:

-   a. purifying monoclonal antibodies obtained from various clones    originating from cell lines selected from hybridomas, in particular    heterohybridomas, and animal or human cell lines transfected with a    vector comprising the gene encoding said antibody;-   b. adding each antibody obtained in step a) to a different reaction    mixture comprising:    -   the target cells for said antibodies,    -   effector cells comprising cells expressing FcγRIII,    -   polyvalent IgGs;-   c. determining the percentage lysis of the target cells and    selecting the monoclonal antibodies which activate the effector    cells causing significant lysis of the target cells (FcγRIII-type    ADCC activity).

The clones may originate from heterohybrid cell lines obtained by fusionof human B lymphocytes (originating from immunized individuals) withmurine, human or heterohybrid myeloma cells, in particular the K6H6-B5myeloma (ATCC No. CRL 1823); or else from animal or human cell linestransfected with a vector containing the gene encoding a human IgGimmunoglobulin, said lines possibly being selected in particular fromthe CHO-K, CHO-Lec10, CHO Lec-1, CHO Pro-5, CHO dhfr-, Wil-2, Jurkat,Vero, Molt-4, COS-7, 293-HEK, YB2/0, BHK, K6H6, NSO, SP2/0-Ag 14 andP3X63Ag8.653 lines.

The polyvalent IgGs are used to inhibit the mechanism of lysis of theeffector cells via FcγRI. In this method, the antibodies which exhibitan FcγRIII-type ADCC level greater than 60%, 70%, 80%, or preferablygreater than 90%, are selected. The target cells can be red blood cellstreated with papain. In this case, the following are deposited per well:

-   -   100 μl of purified monoclonal antibodies at approximately 200        ng/ml,    -   25 μl of papain-treated red blood cells, i.e. approximately        1×10⁶ cells,    -   25 μl of effector cells, i.e. approximately 2×10⁶ cells,    -   and 50 μl of polyvalent IgGs, in particular of TEGELINE™ (LFB,        France), at a concentration of between 1 and 20 mg/ml.

It is thus possible to compare the amount of target cell lysis to twopositive controls consisting of a chemical compound such as NH₄Cl and areference antibody active in vivo, and to a negative control consistingof an antibody inactive in vivo.

It is also possible to use polyclonal antibodies of commercial origin aspositive controls and a monoclonal antibody incapable of inducingclearance in vivo as a negative control.

Advantageously, this method makes it possible to prepare anti-Rh(D)monoclonal antibodies as indicated above. Rhesus D red blood cells arethen used as target cells.

The invention is therefore based on developing an assay for biologicalactivity in vitro, in which the activities measured correlate with thebiological activity in vivo of the monoclonal or polyclonal antibodiesalready evaluated from the clinical point of view with regard to theirpotentiality in inducing clearance of Rh(D)-positive red blood cells inRh(D)-negative volunteers. This assay makes it possible to evaluate theantibody-dependent lytic activity=ADCC (antibody-dependent cellularcytotoxicity) induced essentially by the Fcγ type III receptors (CD16),the Fcγ type I receptors (CD64) being saturated by the addition of humanIgG immunoglobulins (in the form of therapeutic polyvalent IgGs). TheFcγRIII specificity of this ADCC assay was confirmed by inhibition inthe presence of an anti-FcγRIII monoclonal antibody (see FIG. 6).Mononuclear cells from healthy individuals are used as effector cells inan effector/target (E/T) ratio close to physiological conditions invivo. Under these conditions, the lytic activities of the polyclonalimmunoglobulins and of the anti-D monoclonal antibodies ineffective invivo (antibody DFS, Goossens et al., 1987, and the antibodies AD1+AD3,FR 92/07893 LFB/Biotest and FOG-1, GB 2189506) are, respectively, strongand weak.

The selection of the antibodies described in the present invention wastherefore carried out by evaluating their biological activity in thisADCC-type assay (see example 1).

In another aspect, the invention relates to the antibodies which can beobtained using the method described above, said antibodies exhibitingFcγRIII-type ADCC levels greater than 60%, 70%, 80%, or preferablygreater than 90%, relative to the reference polyclonal. The monoclonalantibodies of the invention, directed against a given antigen, activateeffector cells expressing FcγRIII, causing lysis greater than 60%, 70%,80%, preferably greater than 90%, of the lysis caused by polyclonalantibodies directed against said antigen. Advantageously, saidmonoclonal antibodies are directed against rhesus D.

They may preferably be produced by clones derived from the Vero (ATCCNo. CCL 81), YB2/0 (ATTC No. CRL 1662) or CHO Lec-1 (ATCC No. CRL 1735)lines and may belong to the IgG1 or IgG3 class.

The invention also relates to antibodies which have a particular glycanstructure conferring FcγRIII-dependent effector activity.

Such antibodies can be obtained using a method explained above and have,on their Fcγ glycosylation site (Asn 297), glycan structures of thebi-antennary type, with short chains and a low degree of sialylation.Preferably, their glycan structure exhibits nonintercalated terminalmannoses and/or terminal GlcNAcs.

Such antibodies are more particularly selected from the forms:

Thus, the invention is directed toward a monoclonal antibodycharacterized in that it has, on its Fcγ glycosylation site (Asn 297),glycan structures of the bi-antennary type, with short chains, a lowdegree of sialylation, and nonintercalated mannoses and GlcNAcs with aterminal point of attachment. Said antibodies, directed against a givenantigen, activate effector cells expressing FcγRIII, causing lysisgreater than 60%, 70%, 80%, preferably greater than 90%, of the lysiscaused by polyclonal antibodies directed against said antigen.

More particularly, the invention relates to antibodies and compositionscomprising said antibodies as defined above, in which the sialic acidcontent is less than 25%, 20%, 15% or 10%, preferably 5%, 4%, 3% or 2%.

Similarly, the invention relates to antibodies and compositionscomprising said antibodies as defined above, in which the fucose contentis less than 65%, 60%, 50%, 40% or 30%. Preferably, the fucose contentis between 20% and 45%, or else between 25% and 40%.

A particularly effective composition according to the inventioncomprises, for example, a content greater than 60%, preferably greaterthan 80%, for the G0+G1+G0F+G1F forms, it being understood that theG0F+G1F forms are less than 50%, preferably less than 30%.

TABLE 1 Quantification (%) of the oligosaccharide structures of thevarious anti-RhD antibodies Antibodies inactive by Antibodies active byFcRγIII ADCC FcRγIII ADCC R297 R270 F60 D31 HPCE- HPCE- HPCE- HPCE-HPCE- F5 Structure LIF LIF HPLCs LIF HPLCs LIF LIF HPLCs Fucosylated34.3 45.9 37.2 47.7 46.6 82.0 88 100 Sialylated 1.0 2.2 4.1 9.9 19.647.9 52.0 17 G2S2FB 2.8 G2S2F 0.0 0.0 n.d. 4.2 0.0 11.3 11.9 4.1 G2S1FB6.1 G2S1F 1.0 1.0 n.d. 2.7 2.5 21.4 30.5 28 G2S1 0.0 1.2 n.d. 3.0 0.0 00 G1S1FB 6.2 G1S1F 1.7 G2F 3.9 5.0 3.0 10.3 11.6 16.9 22.1 4.2 G2 12.16.1 3.3 7.0 13.3 2.0 0.0 0.0 G1FB 25.7 G1F 17.4 16.9 15 24.8 22.1 16.121.5 12.4 G1 26.1 11.3 21.0 22.2 22.8 0.0 0.0 0.0 G0F 12.1 23.1 19.4 5.610.5 1.7 3.0 0.0 G0 29.1 32.7 38.5 15.8 17.7 13.6 13.9 0.5

An alternative for specifically targeting FcγRIII consists in preparingantibodies of the “high mannose” type.

In another aspect, the invention relates to a cell producing an antibodymentioned above. It may be a hybridoma, in particular a heterohybridomaobtained with the fusion partner K6H6-B5 (ATCC No. CRL 1823); or ananimal or human cell transfected with a vector comprising the geneencoding said antibody, in particular a cell derived from the Vero (ATCCNo. CCL 81), YB2/0 (ATCC No. CRL 1662) or CHO Lec-1 (ATCC No. CRL 1735)lines. These cells correspond to the cell lines selected using themethod according to the invention, said cells producing antibodies whichhave the characteristics mentioned above.

A preferred antibody according to the invention shows considerablebiological activity (greater than or equal to that of the anti-Rh(D)reference polyclonal antibody) in the ADCC assay using FcγRIII-positiveeffector cells.

Its ability to activate FcγRIII receptors (after binding) is confirmedon in vitro models which demonstrate modification of intracellularcalcium flux, phosphorylation of activation signal transductionmolecules, or release of chemical mediators.

These properties are associated with a particular structure of theoligosaccharides of the N-glycosylation site of the Fc component of theantibody: presence of short chains, low degree of galactosylation,little sialylation, may have non-intercalated terminal mannoses and/orterminal GlcNAcs, for example.

This antibody has therapeutic applications: prevention of HDN, treatmentof ITP in Rh(D)-positive individuals, and any other application to whichthe use of anti-D polyclonal immunoglobulins relates.

A preferred antibody according to the invention may also have aspecificity other than anti-Rh(D) (anti-cancer cell for example). It mayhave the properties described above (functional activity dependent on amechanism of binding to/activation of FcγRIII receptors, particularstructure of oligosaccharides) and may be used in immunotherapy forcancers or for any other pathological condition for which a curative orpreventive treatment may be carried out using a monoclonal antibody themechanism of action of which corresponds to an activity which isfunctional via the FcγRIII receptor.

Another aspect relates to a pharmaceutical composition comprising anantibody according to the invention and to the use of said antibody forproducing a medicinal product.

Preferably, the invention relates to the use of an anti-Rh(D) antibodydescribed above, for producing a medicinal product intended for theprevention of Rhesus alloimmunization of Rh-negative individuals. Themethod of action of the anti-D immunoglobulins in vivo is specificbinding of the antibodies to the D antigen of the Rh(D)-positive redblood cells, followed by elimination of these red blood cells from thecirculation essentially in the spleen. This clearance is associated witha dynamic mechanism of suppression of primary immune response in theindividual, and therefore prevents the immunization.

Thus, an antibody of the invention may be used prophylactically forpreventing alloimmunization of Rhesus-negative women immediately afterthe birth of a Rhesus-positive child, and for preventing, at the time ofsubsequent pregnancies, hemolytic disease of the newborn (HDN); at thetime of abortions or of extra-uterine pregnancies in a situation ofRhesus D incompatibility or else at the time of transplacentalhemorrhages resulting from amniocentesis, from chorionic biopsies orfrom traumatic obstetric manipulations in a situation of Rhesus Dincompatibility.

In addition, an antibody of the invention may be used in the case ofRh-incompatible transfusions with blood or labile blood derivatives.

The invention also relates to the use of an antibody of the inventionfor producing a medicinal product intended for therapeutic use inIdiopathic Thrombocytopenic Purpura (ITP).

The antibodies of the invention are also of use for producing amedicinal product intended for the treatment of cancers byimmunotherapy, or for the treatment of infections caused by viral orbacterial pathogenic agents.

An additional aspect of the invention relates to the use of saidantibodies in particular for diagnosis. The invention is thereforedirected toward a kit comprising an antibody described above.

For the remainder of the description, reference will be made to thelegends of the figures presented below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: ADCC evaluation of F60 and T125 YB2/0 (R270). This figurerepresents the percentage lysis obtained as a function of the antibodyconcentration in the presence of 100 and 500 μg/well of TEGELINE™ (LFB,France). A high percentage lysis is obtained for the antibodiesaccording to the invention F60 and T125.

FIG. 2: Anti-D binding to the receptor (FcγRIII). A high binding indexis obtained for the antibodies according to the invention F60 and T125.

FIG. 3: Construction of the expression vector T125-H26 for expressingthe H chain of T125.

FIG. 4: Construction of the expression vector T125-K47 for expressingthe L chain of T125

FIG. 5: Construction of the expression vector T125-IG24 for expressingthe whole antibody T125

FIG. 6: ADCC inhibition in the presence of anti-FcRIII (CD16)

The ADCC assay is established according to the procedure described in§3.3 in the presence of the commercial anti-CD16 3G8 (TEBU), the actionof which is to block the FcRIII receptors present on the effector cells.The final concentration of 3G8 is 5 μg/well (25 μg/ml). A control iscarried out in parallel in the absence of 3G8.

The three antibodies tested are Poly-D WinRho, the antibody F60 (Pf 15599/47) obtained according to the method described in example I, and R297(Pf 210 01/76) obtained according to the method described in example II.

Results: an inhibition is observed in the presence of 3G8, whichdemonstrates that the ADCC induced by the three antibodies tested ismainly FcRIII-dependent. A slightly stronger inhibition is observed inthe presence of Poly-D WinRho (83% compared to 68% and 61% inhibitionfor F60 and 8297, respectively). This difference may be due to thepresence, in the Poly-D, of non-anti-D human IgGs which will inhibittype I receptors (FCRI or CD64) and therefore act synergistically withthe anti-CD 16.

FIG. 7: Characterization of the anti-D glycans by mass spectrometry(MS).

FIG. 8: Comparison of the MS spectra for R290 and DFS.

FIG. 9: Study of the glycosylation of the anti-D D31DMM by MS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Establishinga Heterohybrid Cell Line Producing

An Anti-Rh(D) Antibody

1—Production of Lymphoblastoid and Heterohybrid Clones: 1.1—LymphocyteSource:

The B lymphocyte donor is selected from anti-Rh(D) donors undergoingplasmapheresis, based on the activity of his or her anti-Rh(D) serumantibodies in the ADCC activity assay described in §33. After a wholeblood donation, in 1998, the “buffy coat” fraction (leukocyteconcentrate) was recovered.

1.2—Immortalization of the B Lymphocytes from the Donor

The peripheral blood mononuclear cells are separated from the otherelements by centrifugation on Ficoll Plus (Pharmacia). They are thendiluted to 10⁶ cell/ml in IMDM containing 20% (v/v) of fetal calf serum(FCS), to which 20% of culture supernatant of the B95-8 line(ATCC-CRL1612), 0.1 μg/ml of cyclosporin A (Sandoz), 50 μg/ml ofgentamycin sulfate (Life Technologies) are added, and distributed intoround-bottomed 96-well plates or 24-well plates (P24 Greiner). They arethen placed in an incubator at 37° C., 7% CO₂. After 3 weeks, thepresence of anti-Rh(D) antibodies is sought by ADCC.

Each one of the 16 microwells of a positive P24 plate well istransferred into a new P24 well. This enrichment is repeated after 10 to15 days of culturing and each microwell is amplified in a P96 and thenin a P24.

The positive P96 wells are taken up and amplified in a flat-bottomed P24(Nunc). After a few days of culturing, the presence of anti-Rh(D)antibodies is sought by ADCC.

1.3—Enrichment by Immunorosetting (IR):

The cells derived from one or more P24 wells are enriched in specificcells by the formation and separation of rosettes with papain-treatedRh(D)-positive red blood cells: one volume of red blood cells washed in0.9% NaCl is incubated for 10 minutes at 37° C. with 1 volume of papain(Merck) solution at 1/1 000th (m/v), and then washed 3 times in 0.9%NaCl. The cells were then washed once in Hanks solution, suspended inFCS and mixed with the papain-treated red blood cells in a ratio of 1cell to 33 red blood cells. The mixture is placed in a cone-bottomedcentrifuged tube, centrifuged for 5 minutes at 80 g and incubated forone hour in melting ice. The mixture is then carefully agitated andFicoll is deposited at the bottom of the tube for separation at 900 gfor 20 minutes. The pellet containing the rosettes is hemolyzed in asolution of NH₄Cl for 5 minutes and the cells are placed in cultureagain in a P24 containing irradiated human mononuclear cells. Afterapproximately 1 week, the supernatants are evaluated in CELA (paragraph3.2) and ADCC assays for the presence of anti-Rh(D) antibodies havinggood activity. A further cycle of enrichment is carried out if thepercentage of cells forming rosettes significantly increases compared tothe preceding cycle.

1.4—Cloning of the Lymphoblastoid Cells:

The IR-enriched cells are distributed at 5 and 0.5 cells per well inround-bottomed 96-well plates containing irradiated human mononuclearcells.

After approximately 4 weeks of culturing, the supernatants from thewells containing cell aggregates are evaluated by ADCC assay.

1.5—Heterofusion:

The wells from cloning the EBV-transformed cells exhibiting anadvantageous ADCC activity are amplified in culture and then fused withthe heteromyeloma K6H6-B5 (ATCC CRL-1823) according to the standard PEGtechnique. After fusion, the cells are distributed, in a proportion of2×10⁴ cells/well, into flat-bottomed P96s containing murineintraperitoneal macrophages and in a selective medium containingaminopterin and ouabain (Sigma).

After 3 to 4 weeks of culturing, the supernatants of the wellscontaining cell aggregates are evaluated by ADCC assay.

1.6—Cloning of the heterohybridomas:

Cloning by limiting dilution is carried out at 4, 2 and 1 cell/well inflat-bottomed P96s. After 2 weeks, the microscopic appearance of thewells is examined in order to identify the single clones, and the mediumis then renewed. After approximately 2 weeks, the supernatants of thewells containing cell aggregates are evaluated by ADCC assay.

2—History of the Clones Selected:

2.1—Clone producing an IgG1

EBV transformation of the cells of donor d13 made it possible to selecta well, designated T125 2A2, on which the following were successivelycarried out: 2 enrichments, 3 cycles of IR, and cloning at 5 cells/wellto give 2 clones:

-   1) T125 2A2 (5/1)A2 from which the DNA was extracted in order to    prepare the recombinant vector;-   2) T125 (5/1)A2 which was fused with K6H6-B5 to give F60 2F6 and    then, after 5 rounds of cloning, F60 2F6 (5) 4C4, a clone selected    for constituting a cell stock prior to preparing libraries.

It is an IgG1 possessing a Kappa light chain

2.2—Clone producing an IgG3

A line producing an IgG3 was prepared according to the same method asthat used to prepare the antibody of IgG1 isotype. The cells of originoriginate from a donation of whole blood, from a designated donor, fromwhich the “buffy coat” fraction (leukocyte concentrate) was recovered.

It is an IgG3 possessing a Kappa light chain.

3—Methods for Evaluating the Anti-Rh(D) Antibodies:

After purification by affinity chromatography on protein A sepharose(Pharmacia) and dialysis in 25 mM Tris buffer, 150 mM NaCl, pH 7.4, theconcentration of the antibody T125 is determined by the ELISA technique.The biological activity in vitro is then measured by the ADCC technique.

3.1—Determination of the IgG Level and of the Isotypes by the ELISATechnique:

Total IgGs

Coating: anti-IgG (Calbiochem) at 2 μg/ml in 0.05M carbonate buffer, pH9.5, overnight at 4° C. Saturation: dilution buffer (PBS+1% BSA+0.05%Tween 20, pH 7.2), 1 h at ambient temperature. Washing (to be renewed ateach step): H₂O+150 mM NaCl+0.05% Tween 20. Dilution of the samples, indilution buffer to approximately 100 ng/ml and of the control range madeup of LFB polyvalent human IgGs prediluted to 100 ng/ml. Incubation for2 h at ambient temperature. Conjugate: anti-IgG (Diagnostic Pasteur)diluted to 1/5 000, 2 hours at ambient temperature. Substrate: OPD at0.5 mg/ml (Sigma) in phosphate-citrate buffer containing sodiumperborate (Sigma), 10 minutes in the dark. Reaction stopped with 1N HCl,and read at 492 nm.

Assaying of Kappa Chain

Coating: anti-Kappa (Caltag Lab) at 5 μg/ml in 0.05M carbonate buffer,pH 9.5, overnight at 4° C. Saturation: dilution buffer (PBS+1% BSA+0.05%Tween 20, pH 7.2), 1 h at ambient temperature. The washing (to berenewed at each step): H₂O+150 mM NaCl+0.05% Tween 20. Dilution of thesamples, in dilution buffer, to approximately 100 ng/ml and of thecontrol range made up of the LFB monoclonal antibody AD3T1 (Kappa/gamma3) prediluted to 100 ng/ml. Incubation for 2 h at ambient temperature.Conjugate: biotinylated anti-Kappa (Pierce) diluted to 1/1 000 in thepresence of streptavidin-peroxidase (Pierce) diluted to 1/1 500, 2 hoursat ambient temperature. Substrate: OPD at 0.5 mg/ml (sigma) inphosphate-citrate buffer containing sodium perborate (Sigma), 10 minutesin the dark. The reaction is stopped with 1N HCl, and read at 492 nm.

3.2—Specific Assaying of Anti-D by the CELA (Cellular Enzyme LinkedAssay) Technique:

This method is used for specifically assaying the anti-D antibodies inparticular when this involves a culture supernatant at culturing stagesat which other non-anti-D immunoglobulins are present in the solution(early stages after EBV transformation).

Principle:

The anti-D antibody is incubated with Rhesus-positive red blood cellsand then revealed with an alkaline phosphatase-labeled anti-human Ig.

100 μl of Rh+ red blood cells at 10% diluted in Liss-1% BSA dilutionbuffer. Dilution of the samples, in dilution buffer, to approximately500 ng/ml and of the control range made up of a purified monoclonalhuman anti-D IgG (DFS, LFB) prediluted to 500 ng/ml. Incubation for 45min at ambient temperature. Washing (to be renewed at each step):H₂O+150 mM NaCl. Conjugate: anti-IgG alkaline phosphatase (Jackson)diluted to 1/4 000 in PBS+1% BSA, 1 h 30 at ambient temperature.Substrate: PNPP at 1 mg/ml (sigma) in 1M diethanolamine, 0.5 mM MgCl₂,pH 9.8. The reaction is stopped with 1N NaOH, and read at 405 nm.

3.3—ADCC Technique

The ADCC (antibody-dependent cellular cytotoxicity) technique makes itpossible to evaluate the ability of the (anti-D) antibodies to inducelysis of Rh-positive red blood cells, in the presence of effector cells(mononuclear cells or lymphocytes).

Briefly, the red blood cells of an Rh-positive cell concentrate aretreated with papain (1 mg/ml, 10 min at 37° C.) and then washed in 0.9%NaCl. The effector cells are isolated from a pool of at least 3buffy-coats, by centrifugation on Ficoll (Pharmacia), followed by a stepof adhesion in the presence of 25% FCS, so as to obtain alymphocyte/monocyte ratio of the order of 9. The following aredeposited, per well, into a microtitration plate (96 well): 100 μl ofpurified anti-D antibody at 200 ng/ml, 25 μl of Rh+ papain-treated redblood cells (i.e. 1×10⁶), 25 μl of effector cells (i.e. 2×10⁶) and 50 μlof polyvalent IgG (Tegeline, LFB, for example) at the usualconcentrations of 10 and 2 mg/ml. The dilutions are made in IMDMcontaining 0.25% FCS. After overnight incubation at 37° C., the platesare centrifuged, and the hemoglobin released into the supernatant isthen measured in the presence of a substrate specific for peroxidaseactivity (2,7-diaminofluorene, DAF). The results are expressed aspercentage lysis, 100% corresponding to total red blood cell lysis inNH₄Cl (100% control), and 0% to the reaction mixture without antibody(0% control).

The specific lysis is calculated as a percentage according to thefollowing formula:

$\frac{\left( {{{OD}\mspace{14mu} {sample}} - {{OD}\mspace{14mu} 0\% \mspace{14mu} {control}}} \right) \times 100}{{{OD}\mspace{14mu} 100\% \mspace{14mu} {control}} - {{OD}\mspace{14mu} 0\% \mspace{14mu} {control}}} = {\% \mspace{14mu} {ADCC}}$

The results given in FIG. 1 show the activity of the antibody producedby the heterohybrid F60 compared to those of the reference antibodies:

the anti-Rh(D) polyclonal antibodies POLY-D LFB 51 and WinRhO W03(Cangene)=positive controls

the monoclonal antibody DF5 (inactive in vivo on clearance ofRh(D)-positive red blood cells (BROSSARD/FNTS, 1990, notpublished))=negative control

the IgG1s purified (separated from the IgG3s) from the polyclonal WinRhOW03.

Two concentrations of human IgGs (Tegeline LFB) are used to show thatinhibition of activity of the negative control is linked to the bindingof competing IgGs to the Fcγ type I receptors.

3.4—FcγRIII(CD16)-binding technique:

This assay makes it possible to assess the binding of the anti-Rh(D)antibodies of IgG1 isotype to FcγRIII, and in particular todifferentiate IgG3 antibodies. Given the low affinity of this receptorfor monomeric IgGs, prior binding of the antibodies to the D antigen isnecessary.

Principle:

The antibody to be tested (anti-D) is added to membranes of Rh+ redblood cells coated with a microtitration plate, followed by transfectedJurkat cells expressing the FcγRIII receptor at their surface. Aftercentrifugation, the “Rh+ membrane/anti-D/CD16 Jurkat” interaction isvisualized by a homogeneous plating of the CD16 Jurkats in the well. Inthe absence of interaction, the cells are, on the contrary, grouped atthe center of the well. The intensity of the reaction is expressed asnumbers of +.

Method:

1) Incubation for 1 h at 37° C. of the anti-D antibody (50 μl at 1 μg/mlin IMDM) on a Capture R plate (Immunochim), and then washes in water+0.9% NaCl. Addition of CD16 Jurkat (2×10⁶ cells/ml) in IMDM+10% FCS.Incubation for 20 min at 37° C. and then centrifugation and evaluationof cell adhesion (against a control range).

2) Revelation of the anti-D bound to the Capture R plates by anELISA-type technique using anti-human IgG-peroxidase at 1/5 000 (SanofiDiagnostics Pasteur) after having lysed the CD16 Jurkat cells with 0.2MTris-HCl, 6M urea, pH 5.3-5.5. OPD revelation and then reading ofoptical density (O.D.) at 492 nm.

Expression of results: an arbitrary value of 0 to 3 is allotted as afunction of the binding and of the plating of the CD16 Jurkat cells.These values are allotted at each OD interval defined (increments of0.1). The following are plotted:

either a curve: adhesion of the Jurkat cells (Y) as a function of theamount of anti-D bound to the red blood cell membranes (X).

or a histogram of the “binding indices” corresponding, for eachantibody, to the sum of each Jurkat cell binding value (0 to 3) allottedper OD interval (over a portion common to all the antibodies tested).

An example of a histogram is given in FIG. 2.

The anti-Rh(D) antibodies of IgG1 isotype (F60 and T125 YB2/0) show abinding index close to that of the polyclonal IgG1s (WinRho), whereasthe negative control antibodies DF5 and AD1 do not bind. Similarly, theantibody of IgG3 isotype (F41) exhibits a good binding index, slightlyless than that of the IgG3s purified from the polyclonal Winrho andgreater than that of the antibody AD3 (other IgG3 tested and ineffectivein clinical trial, in a mixture with AD1 (Biotest/LFB, 1997, notpublished).

Example 2 Production of a Recombinant Anti-D Antibody (Ab)

1—Isolation and Amplification of the cDNAs Encoding the Heavy and LightChains of the Ab1.1—RNA Extraction and cDNA Synthesis

The total RNAs were extracted from an anti-D Ab-producing clone (IgGG1/Kappa) obtained by EBV transformation: T125 A2 (5/1) A2 (seeparagraph 2, example 1).

The corresponding cDNAs were synthesized by reverse transcription of thetotal RNAs using oligo dT primers.

1.2—Amplification of the Variable Region of the Heavy Chain of T125-A2:VH/T125-A2 Sequence

The VH/T125-A2 sequence is obtained by amplification of the T125-A2cDNAs using the following primers:

-   -   primer A2VH5, located 5′ of the leader region of the VH gene of        T125-A2, introduces a consensus leader sequence (in bold)        deduced from leader sequences already published and associated        with VH genes belonging to the same VH3-30 family as the VH gene        of T125-A2; this sequence also comprises an Eco RI restriction        site (in italics) and a Kozak sequence (underlined):

A2VH5 (SEQ ID No. 1): 5′-CTCTCCGAATTC GCCGCCACCATGGAGTTTGGGCTGAGCTGGGT-3′

-   -   antisense primer GSP2ANP, located 5′ of the constant region (CH)        of T125-A2:

GSP2ANP (SEQ ID No. 2): 5′-GGAAGTAGTCCTTGACCAGGCAG-3′.1.3—Amplification of the constant region of T125-A2: CH/T125-A2 sequence

The CH/T125-A2 sequence is obtained by amplification of the T125-A2cDNAs using the following primers:

-   -   primer G1, located 5′ of the CH region of T125-A2:

G1 (SEQ ID No. 3): 5′-CCCTCCACCAAGGGCCCATCGGTC-3′

-   -    The first G base of the CH sequence is here replaced with a C        (underlined) in order to recreate, after cloning, an Eco RI site        (see paragraph 2.1.1).

antisense primer H3′Xba, located 3′ of the CH of T125-A2, introduces anXba I site (underlined) 3′ of the amplified sequence:

H3'Xba (SEQ ID No. 4): 5′-GAGAGGTCTAGACTATTTACCCGGAGACAGGGAGAG-3′1.4—Amplification of the Kappa light chain: K/T125-A2 sequence

The entire Kappa chain of T125-A2 (K/T125-A2 sequence) is amplified fromthe T125-A2 cDNAs using the following primers:

-   -   primer A2VK3, located 5′ of the leader region of the VK gene of        T125-A2, introduces a consensus sequence (in bold) deduced from        the sequence of several leader regions of VK VH genes belonging        to the same VK1 subgroup as the VK gene of T125-A2; this        sequence also comprises an Eco RI restriction site (in italics)        and a Kozak sequence (underlined):

A2VK3 (SEQ ID No. 5): 5′-CCTACCGAATTC GCCGCCACCATGGACATGAGGGTCCCCGCTCA-3′

-   -   antisense primer KSE1, located 3′ of Kappa, introduces an Eco RI        site (underlined):

KSE1 (SEQ ID No. 6): 5′-GGTGGTGAATTCCTAACACTCTCCCCTGTTGAAGCTCTT-3′.

FIG. 1 gives a diagrammatic illustration of the strategies foramplifying the heavy and light chains of T125-A2.

2—Construction of Expression Vectors 2.1—Vector for Expressing the HeavyChain of T125-A2: T125-H26

The construction of T125-H26 is summarized in FIG. 2. It is carried outin two stages: first of all, construction of the intermediate vectorV51-CH/T125-A2 by insertion of the constant region of T125-A2 into theexpression vector V51 derived from pCI-neo (FIG. 3) and then cloning ofthe variable region into V51-CH/T125-A2.

2.1.1—Cloning of the Constant Region of T125-A2

The amplified CH/T125-A2 sequence is inserted, after phosphorylation, atthe Eco RI site of the vector V51 (FIG. 3). The ligation is performedafter prior treatment of the Eco RI sticky ends of V51 with the Klenowpolymerase in order to make them “blunt-ended.”

The primer G1 used for amplifying CH/T125-A2 makes it possible torecreate, after its insertion into V51, an Eco RI site 5′ of CH/T125-A2.

2.1.2—Cloning of the Variable Region of T125-A2

The VH/T125-A2 sequence obtained by amplification is digested with EcoRI and Apa I and then inserted at the Eco RI and Apa I sites of thevector V51-G1/T125-A2.

2.2—T125-A2 Light Chain Vector: T125-K47

The construction of T125-K47 is given in FIG. 4. The K/T125-A2 sequenceobtained by PCR is digested with Eco RI and inserted at the Eco RI siteof the expression vector V47 derived from pCI-neo (FIG. 5).

2.3—T125-A2 Heavy and Light Chain Vector: T125-1G24

The construction of T125-IG24 is illustrated diagrammatically in FIG. 6.This vector, which contains the two transcription units for the heavyand Kappa chains of T125-A2, is obtained by inserting the Sal I-Xho Ifragment of T125-K47, containing the transcription unit for K/T125-A2,at the Xho I and Sal I sites of T125-H26.

Thus, the heavy and light chains of T125-A2 are expressed under thecontrol of the CMV promoter; other promoters may be used: RSV, IgG heavychain promoter, MMLV LTR, HIV, β-actin, etc.

2.4—T125-A2 Heavy and Light Chain Specific Leader Vector: T125-LS4

A second vector for expressing T125-A2 is also constructed, in which theconsensus leader sequence of the Kappa chain is replaced with the realsequence of the leader region of T125-A2 determined beforehand bysequencing products from “PCR 5′-RACE” (Rapid Amplification of cDNA 5′Ends).

The construction of this T125-LS4 vector is described in FIG. 7. It iscarried out in two stages: first of all, construction of a new vectorfor expressing the T125-A2 Kappa chain, T125-KLS18, and then assembly ofthe final expression vector, T125-LS4, containing the two heavy chainand modified light chain transcription units.

2.4.1—Construction of the Vector T125-KLS18

The 5′ portion of the Kappa consensus leader sequence of the vectorT125-K47 is replaced with the specific leader sequence of T125(KLS/T125-A2) during a step of amplification of the K/T125-A2 sequencecarried out using the following primers:

-   -   primer A2VK9, modifies the 5′ portion of the leader region (in        bold) and introduces an Eco RI site (underlined) and also a        Kozak sequence (in italics):

A2VK9: 5′-CCTACCGAATTC GCCGCCACC ATGAGGGTCCCCGCTCAGCTC-3′

-   -   primer KSE1 (described in paragraph 1.4)

The vector T125-KLS18 is then obtained by replacing the Eco RI fragmentof T125-K47, containing the K/T125-A2 sequence of origin, with the newsequence KLS/T125-A2 digested via Eco RI.

2.4.2—Construction of the Final Vector T125-LS4

The Sal I-Xho I fragment of T125-KLS18, containing the modifiedKLS/T125-A2 sequence, is inserted into T125-H26 at the Xho I and Sal Isites.

3—Production of Anti-D Abs in the YB2/0 Line 3.1—Without GeneAmplification

The two expression vectors T125-IG24 and T125-LS4 were used to transfectcells of the YB2/0 line (rat myeloma, ATCC line No. 1662). Aftertransfection by electroporation and selection of transformants in thepresence of G418 (neo selection), several clones were isolated. Theproduction of recombinant anti-D Abs is approximately 0.2 ng/10⁶cells/24 h (value obtained for clone 3B2 of R270). The ADCC activity ofthis recombinant Ab is greater than or equal to that of the poly-Dcontrols (FIG. 1). The Abs produced using the two expression vectors arenot significantly different in terms of level of production or of ADCCactivity.

3.2—With Gene Amplification

The gene amplification system used is based on the selection oftransformants resistant to methotrexate (MTX). It requires the priorintroduction of a transcription unit encoding the DHFR (dihydrofolatereductase) enzyme into the vector for expressing the recombinant Ab(SHITARI et al., 1994).

3.2.1—Construction of the Expression Vector T125-Dhfr 13

The scheme shown in FIG. 8 describes the construction of the vector forexpressing T125-A2, containing the murine dhfr gene.

A first vector (V64) was constructed from a vector derived from pCI-neo,V43 (FIG. 9), by replacing, 3′ of the SV40 promoter and 5′ of asynthetic polyadenylation sequence, the neo gene (Hind III-Csp 45 Ifragment) with the cDNA of the murine dhfr gene (obtained byamplification from the plasmid pMT2). This vector is then modified so asto create a Cla I site 5′ of the dhfr transcription unit. The Cla Ifragment containing the dhfr transcription unit is then inserted at theCla I site of T125-LS4.

3.2.2—Selection in the Presence of MTX

1st Strategy:

YB2/0 cells transfected by electroporation with the vector T125-dhfr13are selected in the presence of G418. The recombinant Ab-producingtransformants are then subjected to selection in the presence ofincreasing doses of MTX (from 25 nM to 25 μM). The progression of therecombinant Ab production, reflecting the gene amplification process, isfollowed during the MTX selection steps. The MTX-resistant transformantsare then cloned by limiting dilution. The level and the stability of therecombinant Ab production are evaluated for each clone obtained. Theanti-D antibody productivity after gene amplification is approximately13 (+/−7) μg/10⁶ cells/24 h.

2nd Strategy:

YB2/0 cells transfected by electroporation with vector T125-dhfr13 areselected in the presence of G418. The best recombinant Ab-producingtransformants are cloned by limiting dilution before selection in thepresence of increasing doses of MTX. The progression of the productionby each clone, reflecting the gene amplification process, is followedduring the MTX selection steps. The level and the stability of therecombinant Ab production are evaluated for each MTX-resistant cloneobtained.

4—Evaluation of the Activity of the T125 Antibody Expressed in YB2/0

After purification by affinity chromatography on protein A Sepharose(Pharmacia) and dialysis into 25 mM Tris buffer, 150 mM NaCl, pH 7.4,the concentration of the T125 antibody is determined by the ELISAtechnique. The biological activity in vitro is then measured by the ADCCassay described above. The results are given in FIG. 1.

Example 3 Demonstration of the Relationship Between Glycan Structure andFcγRIII-Dependent Activity 1—Cell Culture in the Presence ofDeoxymannojirimycin (DMM)

Several studies describe the effect of enzymatic inhibitors on theglycosylation of immunoglobulins and on their biological activity. Anincrease in ADCC activity is reported by ROTHMAN et al., 1989, thisbeing an increase which cannot be attributed to an enhancement of theaffinity of the antibody for its target. The modification ofglycosylation caused by adding DMM consists of inhibition of the α-1,2mannosidase I present in le Golgi. It leads to the production of agreater proportion of polymannosylated, nonfucosylated structures.

Various anti-Rh(D) antibody-producing lines were brought into contactwith DMM and the functional activity of the monoclonal antibodiesproduced was evaluated in the form of culture supernatants or afterpurification.

The cells (heterohybrid or lymphoblastoid cells) are seeded at between 1and 3×10⁵ cell/ml, and cultured in IMDM culture medium (LifeTechnologies) with 10% of FCS and in the presence of 20 μg/ml of DMM(Sigma, Boehringer). After having renewed the medium 3 times, theculture supernatants are assayed by human IgG ELISA and then by ADCC.

TABLE 2 Effect of culturing in the presence of DMM on the ADCC activityof various anti-Rh(D)s ADCC activity as % of the Minimum dose activityof poly-D LFB51 of DMM Culture Culture in the necessary Samples withoutDMM presence of DMM μg/ml F60 109 113 NT D31 19 87 10 DF5 26 62 20 T125RI(3) 3 72 20 T125-CHO 0 105 5 NT—not tested

-   -   Culturing in the presence of deoxymannojirimycin (DMM) brings a        significant improvement to the ADCC results for the antibodies        previously weakly active, produced by:

a human-mouse hybridoma D31 a human lymphoblastoid line DF5 atransfected murine line T125 in CHO

-   -   The addition of DMM may make it possible to restore the ADCC        activity of an antibody derived from the cloid T125=T125 RI(3)        (described in example 1) and which has lost this activity        through sustained culturing.    -   The strong activity of the antibody produced by the        heterohybridoma F60 (the production of which is described in        example 1) is not modified by culturing in the presence of DMM.

2—Production of Recombinant Anti-D Antibodies by Various Cell Lines:2.1—Preparation of an Expression Vector for the Antibody DF5:

The nucleotide sequence of the antibody DF5, a negative control in theADCC assay, is used to study the transfection of this antibody into somelines, in parallel to transfection of the antibody T125.

The sequences encoding the Ab DF5 are isolated and amplified accordingto the same techniques used for the recombinant Ab T125-A2.

-   -   The corresponding cDNAs are first of all synthesized from total        RNA extracted from the anti-D Ab-(IgG G1/Lambda)-producing clone        2MDF5 obtained by EBV transformation.    -   Amplification of the heavy and light chains is then carried out        from these cDNAs using the primers presented below.    -   Amplification of the variable region of the heavy chain of DF5        (VH/DF5 sequence):

primer DF5VH1, located 5′ of the leader region (in bold) of the VH geneof DF5 (sequence published: L. Chouchane et al.); this primer alsocomprises an Eco RI restriction site (in italics) and a Kozak sequence(underlined):

DF5VH1 (SEQ ID No. 8): 5′CTCTCCGAATTC GCCGCCACC ATGGACTGGACCTGGAGGATCCTCTTTTTGGTGG-3′

antisense primer GSP2ANP, located 5′ of the constant region (CH) alreadydescribed in paragraph 1.2 (example 2).

-   -   Amplification of the constant region CH of DF5 (CH/DF5        sequence): primers G1 and H3′Xba already described in paragraph        1.3 (example 2).    -   Amplification of the Lambda light chain of DF5 (LBD/DF5        sequence):

primer DFSVLBD1, located 5′ of the leader region of the VL gene of DF5,introduces a consensus sequence (in bold) deduced from the sequence ofseveral leader regions of VL genes belonging to the same VL1 subgroup asthe VL gene of 2MDF5; this sequence also comprises an Eco RI restrictionsite (in italics) and a Kozak sequence (underlined):

DF5VLBD1 (SEQ ID No. 9): 5′CCTACCGAATTC GCCGCCACC ATGGCCTGGTCTCCTCTCCTCCTCAC-3′

antisense primer LSE1, located 3′ of Lambda, introduces an Eco RI site(underlined):

LSE1 (SEQ ID No. 10): 5′-GAGGAGGAATTCACTATGAACATTCTGTAGGGGCCACTGTCTT-3′.

-   -   The construction of the vectors for expressing the heavy chain        (DF5-H31), light chain (DF5-L10) and heavy and light chains        (DF5-IG1) of the Ab DF5 is carried out according to a        construction scheme similar to vectors expressing the Ab        T125-A2. All the leader sequences of origin (introduced in the        amplification primers) are conserved in these various vectors.        2.2—Transfection of Various Cell Lines with the Antibodies T125        and DF5

The three expression vectors T125-IG24, T125-LS4 and DF5-IgG1 are usedto transfect cells of various lines: Stable or transient transfectionsare performed by electroporation or using a transfection reagent.

TABLE 3 Cell lines used for the transfection of anti-Rh(D) antibodiesName Reference Cell type CHO-K1 ATCC CCL 61 Chinese hamster ovary(epithelium like) CHO-Lec10 Fenouillet et al., 1996, Chinese hamsterovary (epithelium Virology, 218, 224-231 like) Jurkat ATCC TIB-152 HumanT lymphocyte (T leukemia) Molt-4 ATCC CRL 1582 Human T lymphocyte (acutelymphoblastic leukemia) WIL2-NS ATCC CRL 8155 EBV-transformed human Blymphocyte Vero ATCC CCL 81 African green monkey kidney (fibroblastlike) COS-7 ATCC CRL 1651 SV40-transformed African green monkey kidney(fibroblast like) 293-HEK ATCC CRL 1573 Primary human embryonic kidneytransformed with defective adenovirus 5 DNA YB2/0 ATCC CRL 1662Nonsecreting rat myeloma BHK-21 ATCC CCL 10 Newborn hamster kidney(fibroblast like) K6H6-B5 ATCC CRL 1823 Nonsecreting human-mouseheteromyeloma NSO ECACC 85110503 Nonsecreting mouse myeloma (lymphoblastlike) SP2/0-Ag 14 ECACC 85072401 Nonsecreting mouse × mouse hybridomaCHO Lec-1 ATCC CRL 1735 Chinese hamster ovary CHO dhfr ECACC 94060607Chinese hamster ovary CHO Pro-5 ATCC CRL 1781 Chinese hamster ovaryP3X63 ATCC CRL 1580 Nonsecreting mouse myeloma Ag8.653

After selection of the transformants in the presence of G418 (neoselection), several clones were isolated.

The modification of effector activity of a humanized monoclonal antibodyas a function of the expressing cell has been described by CROWE et al.(1992), with the CHO, NSO and YB2/0 cell lines.

The results obtained here confirm the importance of the expressing cellline with respect to the functional characteristics of the antibody tobe produced. Among the cells tested, only the Vero, YB2/0 and CHO Lec-1lines make it possible to express recombinant anti-Rh(D) monoclonalantibodies with strong lytic activity in the ADCC assay (see example 1and table 4).

TABLE 4 ADCC activity of the antibodies DF5 and T125 obtained bytransfection into various cell lines. The results are expressed aspercentage of the activity of the reference polyclonal antibody: Poly-DLFB 51 Transfected cell lines CHO- CHO- 293- K1 Lec10 Wil-2 Jurkat VeroMolt-4 COS-7 HEK YB2/0 antibodies T125 7 +/− 8 22 +/− 6 3 +/− 5 6 +/− 890 +/− 0 13 +/− 2 16 +/− 114 +/− n = 13 n = 11 n = 12 n = 7 21 n = 1 n =4 13 28 n = 5 n = 12 n = 54 DF5 NT 51 +/− NT NT 72 +/− NT 21 +/− 4 12+/− 94 +/− 19 17 n = 4 14 15 n = 3 n = 5 n = 12 n = 15 Transfected celllines CHO- SP2/0- CHO CHO NSO BHK Lec1 Ag14 K6H6-B5 Pro-5 dhfrP3X63Ag8.653 antibodies T125 6 +/− 8 13 +/− 5 106 +/− 0 +/− 0 9 +/− 8 3+/− 3 13 +/− 8 34 +/− 8 n = 3 n = 4 60 n = 6 n = 3 n = 4 n = 12 n = 9 n= 4

3—Study of the Glycan Structures

Characterization of the glycan structures of the anti-Rh-D antibody wascarried out on four purified products having an ADCC activity (F60, andthree recombinant proteins derived from T125) in comparison with twopurified products inactive or very weakly active in the ADCC assayaccording to the invention (D31 and DF5).

In practice, the oligosaccharides are separated from the protein byspecific enzymatic deglycosylation with PNGase F at Asn 297. Theoligosaccharides thus released are labeled with a fluorophore, separatedand identified by various complementary techniques which allow:

fine characterization of the glycan structures by matrix-assisted laserdesorption ionization (MALDI) mass spectrometry by comparison of theexperimental masses with the theoretical masses.

determination of the degree of sialylation by ion exchange HPLC(GlycoSep C)

separation and quantification of the oligosacharride forms according tohydrophilicity criteria by normal-phase HPLC (GlycoSep N)

separation and quantification of the oligosaccharides by highperformance capillary electrophoresis-laser induced fluorescence(HPCE-LIF).

1) CHARACTERIZATION OF THE GLYCANS OF ACTIVE FORMS

The various active forms studied are F60 and three recombinantantibodies, R 290, R 297 and R 270, derived from T125 and produced inYB2/0. Fine characterization of the glycan structures by massspectrometry (FIG. 7) shows that these forms are all of the bi-antennarytype. In the case of R 270, the major form is of the agalactosylated,nonfucosylated type (G0, exp. mass 1459.37 Da, FIG. 1). Three otherstructures are identified: agalactosylated, fucosylated (G0F at 1605.41Da), monogalactosylated, nonfucosylated (G1 at 1621.26 Da) andmonogalactosylated, fucosylated (G1F at 1767.43 Da) in minor amount.These same four structures are characteristic of R 290, F 60 and R 297(FIG. 1).

These four antibodies which are active in ADCC are also characterized bythe absence of oligosaccharides having a bisecting N-acetylglucosamineresidue.

Quantification of the glycan structures by the various techniques ofHPLC and HPCE-LIF (table 1) confirms the presence of the four formsidentified by mass: G0, G0F, G1 and G1F. The degree of sialylation isvery low, in particular for the recombinant products, from 1 to 9.4%,which is confirmed by the similarity of the mass spectra obtained beforeand after enzymatic desialylation. The degree of fucosylation rangesfrom 34 to 59%.

2) INACTIVE FORMS

The various inactive forms studied are D31 and DFS. Quantification ofthe glycan structures by the various chromatographic and capillaryelectrophoresis techniques (table 1) reveals, for these two antibodies,a degree of sialylation close to 50%, and a degree of fucosylation of 88and 100% for D31 and DFS, respectively. These degrees of sialylation andfucosylation are much higher than those obtained from the active forms.

Characterization of the glycan structures shows that the major form is,for the two antibodies, of the bi-antennary, monosialylated,digalactosylated, fucosylated type (G2S1F, table 1). Thecharacterization by mass spectrometry of D31 (FIG. 7) reveals that theneutral forms are mainly of the monogalactosylated, fucosylated type(G1F at 1767.43 Da) and digalactosylated, fucosylated type (G2F at1929.66 Da).

The inactive antibody DF5 is characterized by the presence ofoligosaccharides having an intercalated GlcNAc residue. In particular,the mass analysis (FIG. 8) reveals the presence of a major neutral formof the monogalactosylated, fucosylated, bisecting, intercalated GlcNActype (G1FB at 1851.03 Da). On the other hand, these structural forms areundetectable or present in trace amounts on the active antibodiesstudied.

The ADCC activity of D31 after the action of DMM increases from 10% to60%. The glycan structures of DMM D31 differ from those of D31 by thepresence of oligomannose forms (Man 5, Man 6 and Man 7) (see FIG. 9).

3) CONCLUSION

The various active antibodies are modified on Asn 297 withN-glycosylations of the bi-antennary and/or oligomannoside type. For thebi-antennary forms, this involves short structures with a very lowdegree of sialylation, a low degree of fucosylation, a low degree ofgalactosylation and no intercalated GlcNAc.

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1.-18. (canceled)
 19. A cell culture producing monoclonal antibodieshaving on the Fcγ glycosylation site (Asn 297, EU numbering)bi-antennary glycan structures, wherein said glycan structures of themonoclonal antibodies have a fucose content less than 55%.
 20. The cellculture of claim 19, wherein the fucose content is less than 50%. 21.The cell culture of claim 20, wherein the fucose content is less than40%.
 22. The cell culture of claim 19, wherein the monoclonal antibodiesare directed against an antigen, and activate effector cells expressingFcγ type III receptors, causing a lysis of target cells presenting theantigen greater than 60% of a lysis caused by polyclonal antibodiesdirected against the antigen.
 23. The cell culture of claim 22, whereinthe antigen is rhesus D.
 24. The cell culture of claim 19, wherein themonoclonal antibodies are directed against an antigen, and activateeffector cells expressing Fcγ type III receptors, causing a lysis oftarget cells presenting the antigen greater than 90% of a lysis causedby polyclonal antibodies directed against the antigen.
 25. The cellculture of claim 24, wherein the antigen is rhesus D.
 26. The cellculture of claim 19, wherein the monoclonal antibodies are IgG1antibodies.
 27. The cell culture of claim 19, wherein the monoclonalantibodies are IgG3 antibodies.
 28. The cell culture of claim 19,wherein said glycan structures of the monoclonal antibodies have asialic acid content of less than 25%.
 29. The cell culture of claim 19,wherein the cell culture comprises a clone produced by transfection of acell line with a gene coding for said monoclonal antibodies.
 30. Thecell culture of claim 29, wherein the cell culture comprises a cloneproduced by transfection of a cell line deposited with the ATCC asaccession number CRL-1662.
 31. The cell culture of claim 19, wherein thecell culture comprises a clone isolated from a cell line transfectedwith a gene coding for said monoclonal antibodies.
 32. The cell cultureof claim 31, wherein the cell culture comprises a clone isolated from acell line deposited with the ATCC as accession number CRL-1662transfected with a gene coding for said monoclonal antibodies.
 33. Thecell culture of claim 19, wherein the fucose content is between 20% and55%.
 34. The cell culture of claim 19, wherein the fucose content isbetween 25% and 55%.
 35. The cell culture of claim 33, wherein saidglycan structures of the purified monoclonal antibodies have a fucosecontent between 20% and 30%.
 36. The cell culture of claim 34, whereinsaid glycan structures of the purified monoclonal antibodies have afucose content between 25% and 30%.
 37. The cell culture of claim 24,wherein the antigen is an infectious disease antigen.
 38. The cellculture of claim 24, wherein the antigen is a cancer antigen.